The manual handling of a plurality of receptacles containing predetermined amounts of sample fluids preparatory to the latter being subjected to numerous analytical tests has heretofore been a problem requiring an inordinate amount of care and dexterity on the part of the persons performing the tests. Where numerous samples are to be prepared from a single specimen, the skill and accuracy of the person in preparing such samples has a profound effect on the correctness of the ultimate test results. The manual aspirating and dispensing of predetermined amounts of the specimen oftentimes inadvertently subjected the specimen and/or sample amounts to contamination.
It has heretofore been known from studies made of various flow patterns or profiles caused by the laminar flow of one fluid into a dissimilar second fluid that the resulting profiles for given fluids under similar operating conditions normally had a characteristic substantially parabolic configuration which occupied a long section of the tubular member, commonly referred to as a mixing region. In situations, however, wherein exact amounts of a fluid are to be aspirated and dispensed for purposes of making accurate test samples, it is imperative that intermixing of the sample fluid with the buffer fluid of a reversible pump be inhibited as much as possible and whatever intermixing occurs within the tubular member should be confined to a very short mixing region. The apparatus herein disclosed is directed towards achieving this result.
Prior devices of this general type have heretofore been provided; however, they have been costly and/or fragile, and have been impractical and incapable of achieving the desired results.